1. Field of the Invention
The present invention relates to doffer wires for use in card clothing. More particularly the present invention relates to doffer wires used in card clothing for doffers utilized in the sliver carding and feeding devices associated with high pile fabric knitting machines.
2. Description of the Prior Art
The prior art has known and used doffer wires as a part of the card clothing of the doffers in sliver high pile fabric knitting machines. The art has also recognized, for some time, that the ability to produce high quality sliver high pile fabrics is dependent on the ability of the knitting needles to remove the desired amount of fibers from the doffer wires. The failure of the knitting needles to remove the proper amount of fiber from the doffer wires not only results in a poor quality fabric but also results in a "dirty" doffer which can lead to additional quality problems and down time for the machine.
The doffer wire of the prior art generally comprises a shank portion and a distal portion which are connected by a knee portion having an angle no greater than 130 degrees. This prior art configuration has been found to be unsatisfactory for current sliver high pile knitting applications, as it has been found that some of the fiber will migrate from the distal portion of the doffer wire toward the shank portion. Thus, the doffer wire is not stripped of all the fiber and a fiber build up or accumulation results.
Formerly in sliver high pile knitting, the fiber or staple of which the sliver was composed was on the order of 11/8" to 11/4" in length. The fibers generally are cut from synthetic filaments and are relatively slippery with respect to each other. In order to ensure that the fibers of the sliver would hold during feeding to and carding at the knitting machine, the filaments from which the fiber staple was cut generally were crimped.
More recently, in order to reduce waste during finishing of the fabric, it has become the practice to use shorter fibers having a length on the order of 3/4". The reduction in fiber length has created two new problems. The first problem being that the shorter fiber length creates greater difficulty in holding the fibers together, both in the sliver rope fed to the carding heads and in the sheet formed on the carding heads as the slivers are fed to the knitting needles. This problem persists even though the fibers are crimped as in the former practice. The second problem created through the use of shorter fiber lengths is the difficulty of obtaining the same selected weight of fabric with the shorter fibers. A greater quantity of fibers must be fed to the needles in order to assure the same fabric weight. This means that there must be more individual fibers per square inch on the doffer to ensure more fibers per needle. This is accomplished by running the doffer at a slower rate, thereby providing a heavier build up of the sheet form of sliver fibers on the doffer wires. As a result of the increased build up, the needle hooks can take more fibers as they "rake" through the doffer wires.
While the former practice of using longer staple fibers sometimes led to a "dirty" doffer, the problem has been compounded with the shorter fibers currently in use. The problem is compounded both by the slower rate of running the doffer and by the use of cohesive agents which are employed to hold the shorter fibers together in the sliver form. The cohesive agent is not an adhesive but is a coating which causes the shorter fibers to cling together and maintain integrity in the sliver. The exact composition of the cohesive agents used is not known, as different mills use different cohesive agents in preparing the slivers and they are treated as trade secrets by the respective mills. However, it is known that the cohesive agents in conjunction with the shorter fibers and the required larger build up of fibers have compounded the problem of a "dirty" doffer.
The cohesive agents, while they are useful for the purposes of maintaining the sliver, make it difficult to rake the heavier concentration of sliver fibers from the doffer wires. The coated fibers tend to compact on the doffer wires and as a result of this cohesion are more difficult to rake. They tend to migrate or work their way into the knee portions of the doffer wires and cause a build up or jamming of fibers at the knee portions. The fiber build up in the knee areas of the doffer wires adversely affects the uniformity of the density of the pile in the fabric being knitted. In addition, the build up frequently causes needle breakage. Thus, in addition to unacceptable fabric there is machine down time to replace broken needles.
The present invention solves these difficulties by providing a doffer wire which is easily stripped by the knitting needle and has substantially no migrating fiber build up.